From: Ann Shumelda Okerson <[log in to unmask]>
Date: Sat, 3 Feb 2018 23:56:42 -0500

PubMed Commons has been a valuable experiment in supporting discussion
of published scientific literature. The service was first introduced
as a pilot project in the fall of 2013 and was reviewed in 2015.
Despite low levels of use at that time, NIH decided to extend the
effort for another year or two in hopes that participation would
increase. Unfortunately, usage has remained minimal, with comments
submitted on only 6,000 of the 28 million articles indexed in PubMed.

While many worthwhile comments were made through the service during
its 4 years of operation, NIH has decided that the low level of
participation does not warrant continued investment in the project,
particularly given the availability of other commenting venues.

https://ncbiinsights.ncbi.nlm.nih.gov/2018/02/01/pubmed-commons-to-be-discontinued/